"We've seen no signs of fatigue and from our point of view there's no reason to be concerned."

Media reports said the Pirelli investigation had allayed the nervous drivers' fears.

But it hasn't stopped rumours Michelin, reportedly backed politically by FIA president Jean Todt, is poised to return to F1 to replace Pirelli in 2014.

The BBC said the French marque has already held talks with the governing body, while a Michelin spokesman confirmed the company is still "interested" in F1 but would want a shift away from the new era of heavy tyre degradation.